Principally land-based telephony infrastructures are largely in place throughout much of the world and provide telephone communication to most metropolitan and rural areas. Land-based telephony infrastructures vary in many ways from country to country. For example, highly industrialized nations tend to have infrastructures of a superior quality with regards to hardware, lines, and service. Many lesser industrialized nations have infrastructures that utilize older types of equipment and lines that cannot perform as well as state-of-the-art-equipment such as Computer Telephony Integration (CTI) telephony switches, fiber optic lines, and other advanced equipment known in the art. Also, highly industrialized nations are capable of devoting vast resources to insure that telephony infrastructures are upgraded as needed, whereas lesser industrialized nations often do not have the resources available for upgrading an older telephony infrastructure.
In those areas of the world where land-based infrastructure either is marginal or simply doesn't exist, a possible solution is what are known as Wireless Local Loop (WLL) systems. In WLL systems base stations connected by broadband telephony links (trunk lines) to telephony switches in a public or private network are each adapted to maintain duplex audio communication with a plurality of remote client stations which are in turn connected to one or a few telephones. In further description the equipment at a client station is called Customer Premises Equipment (CPE). The range of such systems varies according to design and power, but is generally limited by practicality to a few tens of kilometers at the most for each base station. Still, given a network of base stations, telephone service becomes practical for many remote areas where such service would not otherwise be provided.
Another use of WLL systems is as alternative service in areas that are well-served by existing telephony systems. As deregulation continues and competition is further encouraged, WLL systems find a market even in highly structured telephony markets.
A WLL telephony system, as will be more apparent in the descriptions to follow, is a highly engineered electronic system, supporting duplex audio in digital two-way radio. There are several methods and apparatus known in the art for synchronizing signals in broadcast and reception between a base station and a remote CPE in WLL. Among these systems is a timing system known in the art as Time-Division Duplex (TDD). In a TDD system, as in many others, circuitry at each end of the system (base station and CPE) has to be timed and synchronized in relatively short time slices (typically a few milliseconds) such that the receiving circuitry at one station is listening while the sending circuitry at the other is broadcasting, and vice versa, in each time slice. Moreover, typically the synchronization of signals is a function of the separation of any two transmitting and receiving units.
Also typically in such systems, highly engineered Integrated Circuits (ICs) are used to provide the timing protocol and many other functions for coordinating two-way communication, and there are many such ICs commercially available. Such ICs in the art are often called engines, and that terminology is used herein in some instances. Unfortunately, however, existing circuits tend to be highly proprietary, and are adapted to very particular functions and ranges, and are therefore not very adaptable to new systems and uses. For example, an IC designed for a wireless telephone and providing timing for a Time Division Duplex (TDD) system provides timing and synchronization for stations always quite close, such as within a hundred meters or so. The timing and synchronization functions of such an IC are very similar to those needed for a WLL system, except for range-related phenomena. Unfortunately one may not disassemble such an IC and change the timing internally.
What is clearly needed is a method and apparatus for adjusting functional range for a system using a TDD timing IC having fixed timing functions, so the longer range of a WLL system, and other relatively long range systems, may be accommodated, and stations may be served at many different distances from a base station within a maximum radius.